We propose to continue and expand the National Vibrating Probe Facility. This expansion should bring the facility up to full operating capacity and allow us to best serve users throughout the country (as well as abroad). It should also allow us to develop a series of ion-specific vibrating probes and an aerial vibrating probe; to extend our measurements of endogenous ionic currents to certain plasmalemma-free preparations; to continue our collaborative exploration of possible currents through the tips of growing nerves as well as the vegetal poles of various embryos; and to continue training new users and disseminating news of our findings and capacities. The user projects should continue to focus on a wide variety of growing and developing systems as well as mature, functioning epithelia. Moreover, they should include ones of medical as well as basic biological interest, particularly in the general area of wound healing and regeneration.